Compared to all other 8.0 tanks the T-55A is quite frankly better. I know this because I use it and I stomp with it at 8.0. All other 8.0 tanks have either a stab or decent APFSDS, not both at the same time like the T-55A has.
In addition to moving the T-55A to 8.3 it could get a researchable kontact 1 ERA mod (if it needed it). To replace the 8.0 T-55A, a new addition to the tech tree could be a first production “T-55” with no roof MG and limited to APDS while also keeping the stab.
I think this would be a better option and would allow a more gradual technological progression in this BR range.
Moving on to the premium 8.3 T-55AM-1, performance wise it is identical to the T-55AMD in the tech tree which is 8.7. It carries the same ammo and LRF and so on.
The only difference being that one has limited hard kill APS while the other has composite cheek armor. If you ask me that is a fair trade off and shouldnt result in two different BR’s.
Keep in mind these changes also help spread out the tech compression that tanks experience in the 6.7-8.7 BR range. Obviously this wont solve the whole issue but it at least helps a little until gaijin properly addresses this like they have promised in their recent summer road map.